EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Airblast caused by large slope collapses

Ivanna Penna1, Reginald Hermanns1, Pierrick Nicolet1, Odd Andre Morken1, John Dehls1, Vikram Gupta2, and Michel Jaboyedoff3
Ivanna Penna et al.
  • 1Geological Survey of Norway
  • 2Wadia Institute of Himalayan Geology
  • 3Institute of Earth Sciences, University of Lausanne

The sudden impact of a large slope collapse on the ground can cause a high degree of comminution of rocks and trigger an extreme rush of air loaded with particles, called an airblast. The airblast can expand the destructive capacity of a large slope collapse far beyond the run-out of the rock mass. The first airblast event documented in detail occurred in 1881 as consequence of a large collapse at Elm in the Unthertal valley (Switzerland). People being blown over by the air pressure wave were reported. In 2015, two rock avalanche related airblasts occurred in the Himalayas. In March 2015, an airblast in Yumthang valley (Sikkim, India) knocked down and snapped trees 1.4 km away from the impact zone of a rock avalanche. In April 2015, an avalanche triggered by the Gorkha earthquake induced a violent airblast that caused several casualties in Langtang valley. The destruction of stone and wooden houses can be observed in video footage. The damage on trees can be traced over a distance of 3.5 km and 400 m above the impact zone of the avalanche on the opposite slope. The most recent documented event occurred in February 2021 in Chamoli (India), where the flattened forest extends over 20 hectares.

This work presents a back analysis of the April 2015 airblast in the Sikkim Himalayas (India) and compares it with several other airblasts documented around the world. We review the conditions a large slope collapse should meet to cause a significant airblast. We also formulate an equation that links the potential energy of collapses having airborne trajectory to the extent of the related airblast.

How to cite: Penna, I., Hermanns, R., Nicolet, P., Morken, O. A., Dehls, J., Gupta, V., and Jaboyedoff, M.: Airblast caused by large slope collapses, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11604,, 2022.